1. Field of the Invention
The present invention relates to a printer. More specifically, the present invention relates to the technological field of a printer comprising a sheet-holding block which can hold a plurality of printing sheets in a stack, a picking-up block for picking up the printing sheets held by the sheet-holding block one sheet at a time, a transporting block for transporting the printing sheets that have been picked up by the picking-up block, a printing block for performing printing on the printing sheets that have been transported by the transporting block, and a sheet-discharging block for discharging the printing sheets that have been subjected to printing at the printing block.
2. Description of the Related Art
There are printers which perform a printing operation on a printing sheet, such as printing paper or a printing film, by, for example, heat transfer or laser. Such a printer ordinarily comprises a sheet-holding block which can hold a plurality of printing sheets in a stack, a picking-up block for picking up the printing sheets held by the sheet-holding block one sheet at a time, a transporting block for transporting the printing sheets that have been picked up by the picking-up block, a printing block for performing printing on the printing sheets that have been transported by the transporting block, and a sheet-discharging block for discharging the printing sheets that have been subjected to printing by the printing block. In the printer, each of the blocks is disposed inside a housing.
There is a printer of what is called a horizontally-setting type which can be set horizontally so that a printing sheet is transported from the sheet-holding block to the sheet-discharging block with the surface of the printing sheet being faced vertically, and a printer of a horizontally-setting-and-vertically-setting type which can be set horizontally and which can be vertically so that a printing sheet is transported from the sheet-holding block to the sheet-discharging block with the surface of the printing sheet being faced horizontally.
Such a horizontally-setting-and-vertically-setting type can be set in accordance with the space of an installation place, so that it can be installed more freely at the installation place, thereby making it easier to use.
When the printer can be set vertically, installation area can be reduced. In particular, when computed tomography (CT) is carried out at a hospital, a large setting area is not required, so that the printer can be set as an accessory of a shooting device or as an accessory of a computer in a medical examination room. Therefore, this type of printer makes it possible to carry out medical work more quickly and simply.
However, in the related printer, printing sheets are successively transported by a plurality of transport rollers, etc., in the process of transporting them to the printing block by the transporting block by picking them up by the picking-up block from the sheet-holding block, so that the position of the printing sheets transported to the printing block may be shifted with respect to the position of the printing sheets picked up from the sheet-holding block.
When such a shift in position occurs, a missing image results because an image is no longer printed onto the entire sheet at the printing block, a shift in the orientation of an image with respect to the printing sheet occurs, etc.
In the sheet-holding block, a plurality of printing sheets are held in a stack. When the printing sheets are held by the sheet-holding block in a warped state, problems such as the printing sheets being improperly picked up by the picking-up block or the printing sheets being damaged when they are picked up by the picking-up block may occur.
The problems of shifts in the position of the printing sheets and warping of the printing sheets tend to occur particularly when the printer is vertically set so that the printing sheets are transported with their surfaces being faced horizontally.
In the horizontally-setting-and-vertically-setting type which performs a printing operation by scanning a printing sheet by a printing head pushed against a platen roller with the printing sheet being interposed therebetween, the pressures upon the printing sheet when the printer is set horizontally and when the printer is set vertically are different due to the effects of the weight of the printing head. Therefore, when printing is performed with the pressures being different, a printing failure may occur in either one of the horizontally set and vertically set states.